Chapter 5:Chapter 5: Cell Growth and Cell Growth and

DivisionDivision

Mitosis Rap

Where is all the genetic information found in a cell?

• On the genes on the Chromosomes

• Chromosomes are actually strands of DNA and proteins

• If cells were the size of a basketball, your DNA would stretch 40 miles

• We have 6 feet of DNA 6 feet of DNA in each cell!!!!!

Every species has a set number of chromosomes

• Chromosome number: – Number of Chromosomes in a body cell

• Specific for each species of organisms. List– Human – 46Human – 46 – Chimpanzee – 48 – Gorilla – 48 – Potato – 48– Bat – 44– Fruit fly – 8– Mosquito – 6– King Crab – 208– Dog - 78– Horse – 64– Donkey - 62 – Adder’s tongue fern 1,262

How would you duplicate a cell exactly to be certain that both new cells have the identical DNA in each cell?

1. Duplicate the DNA first (this is DNA DNA replicationreplication)

2. Find a way to be certain that the DNA does not get broken or tangled during the process of dividing it into the two new cells

3. Be certain that the new daughter cells will have the exact same set of DNA in each new cell’s nucleus

4. Divide up the cell’s contents. (Cytokinesis)

What would happen if a cell were to just split into two without any advance preparation?

• Imagine trying to divide up pieces of yarn by color if they were all just thrown into a pile together.

–It would take a long time to do this efficiently and accurately.

Instead, it is more efficient to shorten up and then organized the replicated DNA prior to dividing the DNA up evenly into two cells.

This is what happens in The Cell Cycle

Chromosome structureChromosome structure • Before cell division occurs, the DNA is loose in

the nucleus and known as Chromatin Chromatin• DNA starts coiling around proteins called

histoneshistones (like thread on a spool)• DNA shortens up ChromosomeChromosome

Coiling animation• The two identical chromosomes that resulted

from DNA replication will find each other and come together. The two “twins” are called chromatidschromatids & are held together by a centromerecentromere

This strand of DNA is identical to this strand of DNA.

Chromatid

Sister Sister ChromatidsChromatids

Label the structures on the Paired Chromosomes

Why do cells need to reproduce?

• Necessary for:– Repair and replacement of damaged cells– Growth (remember your first baby picture)– Smaller cells are more efficient than are

larger cells.

What would happen to a cell if it continued to grow?

As the size of the cell increases, its volume increases faster than its surface area.

Surface area to volume ratio would decrease.

Makes it difficult to move needed materials in and wastes out of the Makes it difficult to move needed materials in and wastes out of the cell efficiently.cell efficiently.

Calculate the Surface area (Length x width x 6) and Volume (Length3) then the Surface area to Volume ratio (reduce to lowest terms)

The Cell CycleThe Cell Cycle • Entire process that a cell undergoes in cell

division from start to finish.• Cells:

1. grow

2. prepare for division

3. divide to form two daughter cells

4. begin the cell cycle over again.– Cells such as skin, lining of digestive tract and

blood cells go through this process frequently– Introduction

Skin Cells: 20 days

Red Blood Cells: 120 days

Stomach lining cells: 2 days

Brain cells: 30-50 years

Platelets: 10 days

Intestinal lining cells: 3 days

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The Cell The Cell CycleCycle

Divided into 2 parts • InterphaseInterphase– G1 - Cell grows from last cell cycle– S – Synthesis of DNA (DNA makes a copy of

itself)– G2 – Cell growth and gets ready for cell

division– G0 – No cell division – typical of cells like

nerve cells that stop dividing at maturitynerve cells that stop dividing at maturity• MitosisMitosis – – MM phasephase

– Prophase– Metaphase– Anaphase– Telophase– Cytokinesis

How long does the Cell Cycle take in a human cell?

Studies have shown that Studies have shown that the average cell works the average cell works on a on a 24 hr cycle 24 hr cycle as does as does typical cell replication.typical cell replication.Embryonic cells will Embryonic cells will divide every divide every 8 minutes8 minutes!!!!Liver cells could take up Liver cells could take up to a year.to a year.However, many cells will However, many cells will be in Gbe in G00 for long periods for long periods

of time.of time.

InterphaseInterphase • Longest phase in

the Cell Cycle

– over half the time is spent in this phase

• ProphaseProphase – longest phase in Mitosis1. Chromosomes are visible2. Chromatids pair up3. Centrioles (if animal cell) migrate to poles4. Nuclear envelope & nucleolus start to

break down5. Fibers form

Sister Chromatids

Nuclear Membrane &

Nucleolus

Centrioles Fibers

Shorten and Thicken

Begins to break down

Move apart from one another

Form between centrioles (in animal cells)

• MetaphaseMetaphase

– shortest part of Mitosis

1.Sister Chromatids line up on the equator (middle)

Sister Chromatids

Nuclear Membrane

Centrioles Fibers

Become attached to the fibers.

Are moved to middle of cell

Remains dissolved

At opposite ends of cells

Go from the poles to

centromeres

• Anaphase Anaphase – “An away they go!”

1. Chromatids separate

2. Go to opposite poles.

Now called chromosomes!!

1. Fibers shorten up

Sister Chromatids

Nuclear Membrane

Centrioles Fibers

Pulled apart by fibers.

Each chromatid is separate from

its “sister”

Now called a chromosome

Remains dissolved

Still at cell’s poles; Pull each

chromosome toward opposite

ends of the cell

• TelophaseTelophase – “the end” – Final phase

1.Chromosomes reach opposite ends

2.Cell membrane pinches in or Cell plate forms (if plants)

3.Chromosomes uncoil

4.Nuclear membrane & nucleolus reappear

5.Fibers disappear

Sister Chromatids

Nuclear Membrane &

Nucleolus

Cell Membrane

Fibers

Each end of cell has a

complete set of identical

chromosomes.

Begins to reform

Begins to pinch, forming two new cells

Begin to disappear

• CytokinesisCytokinesis Dividing up of cellular

contents.

Occurs simultaneously with Telophase

Mitosis and Cytokinesis

• Cytokinesis differs in animal and plant cells.

In animal cells, the membrane pinches closed.

In plant cells, a cell plate forms.

What was the point of Mitosis?• Results in two identical daughter cellstwo identical daughter cells

• Each cell will have the SAME number of SAME number of chromosomeschromosomes as the original cell

• Each cell will have the SAME function SAME function as the original cells

Mitosis animationsMitosis animationsTry them all!

• http://www.sumanasinc.com/webcontent/animations/content/mitosis.html

• cellsalive.• John Kryk• You tube (really good)• Hybrid (love the music)• http://www.csuchico.edu/~jbell/Biol207/animations/

mitosis.html• Arizona• Movie Clip• McGraw

Mitosis Rap

Mitosis Another

Interphase

Anaphase

Metaphase

Late Prophase

Prophase

Telophase

Checking your understanding MitosisStarting with Prophase, draw a cell undergoing mitosis. Your original cell

has 4 chromosomes.

Make certain to include the nuclear membrane, nucleolus, chromatids, centrioles (animal cell), chromosomes and spindles.

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Give the events occurring in each of the

stages of the Cell CycleCell Cycle

Interphase

Metaphase

Telophase

Anaphase

Prophase

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Cancer cells do not carry out normal, necessary functions.

• Cancer cells are abnormal cell growth due to either a:• malfunction in the Cell Cycle• change in the genes during DNA replication during

the S phase of Interphase

• Cancer cells form disorganized clumps called tumors.• Benign tumors remain clustered and can be removed.• Malignant tumors metastasize, or break away, and can

form more tumors.

Normal cells

Mutated cell

Cancerous cells

Blood cells

• Carcinogens are substances known to promote cancer.• UV radiation• Chemicals such as formaldehyde, asbestos, arsenic, benzene…• Tobacco smoke

• Standard cancer treatments typically kill both cancerous and healthy cells.

Stem cells are unique body cells.• Stem cells have the ability to

– divide and renew themselves– remain undifferentiated in form– develop into a variety of specialized cell types

Some people save the placenta or umbilical cord to harvest these

• The use of stem cells offers many currently realized and potential benefits.

– Stem cells are used to treat leukemia and lymphoma.– Stem cells may cure disease or replace damaged

organs.– Stem cells may revolutionize the drug development

process.

Henrietta LacksHenrietta LacksThe Immortal Hela cellsThe Immortal Hela cells

•Basic Information

•Please Do Now:– Write 4 LINES about your reaction to this video

• Was the action of the scientists right or wrong? Why?• Include at least 1 fact about cancer from your notes

or the video.